Halliday & Matthiessen (2014: 392):
The Premodifier may accommodate both hypotactic word complexes like a very much better argument, and word rank embeddings like a four-post bed, a left-handed batsman; including compressed phrases and clauses like your in-flight magazine, a never-to-be-forgotten experience. The word complexes derive from the potential for logical expansion built into the noun as Head; the embeddings from the functional scope of the experiential configuration into which the noun enters as Thing.
* In the first two editions of IFG, the Postmodifier also was brought into the scope of the logical representation. But this appears to complicate the description without adding further to its explanatory power.